All that follows is a transcript I made of Dr. Weingart’s update podcast #137 remarks so that I would have it available for quick review. It is not in his exact words in some places and therefore everyone needs to listen to the podcast.

So here is my transcription of Dr. Weingart’s podcast:

DSI is part of the four concept package that I’ve been talking about for years. These are new innovations that will help with the airway management in the critically ill patient.

The first is DSI.

The second is CPAP pre-oxygenation.

The third is apneic preoxygenation.

And the fourth is a ventilator instead of our bag mask.

Before we get DSI let’s go over an update on preoxygenation.

The standard non-rebreather mask at 15 L only gets you to about concentration of 60% FI 02 and that’s not enough to de-nitrogenate your patient’s lungs.

Here’s the new recommendation from Rich and I.

Every time you preoxygenation with a non-read breathing mask at 15 L per minute, underneath it should be a nasal cannula running at 15 L per minute.

And those two techniques in combination will get the patient’s FI 02 to well over 90%. So, nasal cannula at 15 and non-rebreather at 15 for all patients being preoxygenation.

If that’s not cutting it, the stats are coming up because they have shut physiology, they need CPAP preoxygenation.

All CPAP preoxygenation is with a nasal cannula at 15 L per minute underneath the CPAP mask.

This allows for ideal preoxygenation. It allows for ideal apneic oxygenation. And obviously if they needed CPAP for preoxygenation, they’ll need it for the apneic period and for the intubation period and for the re-intubation. If you have to do it again.

In other words you want the nasal cannula at 15 mL per minute bonded to the patient’s nose throughout the entire preoxygenation.

Now we are going to get to the DSI stuff.

The classic case of when you use DSI is the patient with horrible saturations and so you know you want to innovate and you keep trying to hold the non-rebreather mask on the patient’s face they keep slapping it away from you. They are fighting you and they won’t let you preoxygenation effectively.

The standard emergency medicine response to this problem is to RSI them and attempt to bag them up during the apneic period. All this leads to stress and possibly a disorganized intubation procedure.

So you have a patient with agitated delirium from say hypoxia, from hypercapnia, from whatever medical condition is needing them to require airway management, and you don’t like it.

So here’s what DSI is:

So you give them a slow push of ketamine (because rapid push ketamine will cause apnea for 10 to 15 seconds).

The dose of ketamine that we recommend is 1 mg per kilogram to start unless you need to take immediate control of the patient (for example, the patient’s just pulled switchblade out of his pocket [meaning there is a critical medical reason that you need to get control immediately]).

You wait 10 to 15 seconds because that’s how quickly ketamine works. And if they are totally chilled out, lying comfortably on the stretcher, no longer fighting you; then you stop [pushing ketamine].

If not, you give another .5 mg per kilogram of ketamine and wait 10 to 15 seconds. If they’re still not adequately sedated you give another .5 mg of ketamine and wait 10 to 15 seconds.

And you keep giving those .5 mg per kilogram aliquots of ketamine until the patient is chilled.

Now the beauty of ketamine is that they will keep breathing unless you push it rapidly. If you push it to rapidly they will go apneic but they will start reading again in 10 to 15 seconds. And they will maintain their airway reflexes.

This now allows you to preoxygenation the patient with a nasal cannula and non-rebreather mask or nasal cannula and CPAP mask if that’s what the patient needs. It’ll allow you to place an NG tube (for example for a massive G.I. bleeder). It will allow you to position the patient. It will allow you the time to get everything set up just the way you like for the intubation procedure.

You will give them the minimum of 3 min. of breathing of the non-rebreather and nasal cannula or CPAP mask and nasal cannula.

Then you will paralyze with succinylcholine or rocuronium. Then you will give them apneic oxygenation [leaving the nasal cannula at 15 L per minute on under the bag mask as you ventilate them].

And then you will intubate safely with a calm atmosphere.

There is a flowchart that you can look at in the show notes for this podcast.

So, now let’s get to the evidence which is in prepublication in the annals of emergency medicine and while it is in prepublication it is available for free. The authors of this paper are [insert names here].

We had 62 patients in a prospective cohort trial. We didn’t put this in the paper but they were essentially self-controlled. Why do I say that?

Here’s the deal: the primary outcome was their best saturation that we could achieve with normal attempts at preoxygenation (holding the mask on the patient’s face [the non-rebreather at 15 L, begging the patient let us hold the mask on them, trying to hold down their hands so they don’t pull the mask off).

So with all that what was the best sat we could get.

And then after pushing the ketamine, what was their saturation just before pushing the muscle relaxant.

So, when you think about that we gave it our best shot in the normal way, trying to get the patient to leave the non-rebreather mask or CPAP mask on. And then we saw how much better we could do with ketamine dissociation. And that was our primary outcome.

You can go to the show notes to see the reason that these patients were intubated (and it was the standard stuff pneumonia, asthma, pulmonary edema, etc.). And you can also see the type of respiratory failure that made us want to select intubate them. We divided goes into type I – oxygen failure, type II– ventilatory failure. And the third situation was for airway protection (it wasn’t that we were worried about oxygenating or ventilating them but rather that they would lose their airway).

Most of these patients were oxygenation failure. About a third of them were for airway protection. And only a few were ventilatory failure.

And that makes sense because for ventilatory issues, BiPAP (noninvasive positive pressure ventilation) has really taken the prominent role. We don’t generally innovate those patients anymore.

And then the reasons for DSI: 31% of patients couldn’t tolerate the non-rebreather mask, 63% because they couldn’t tolerate noninvasive because the non-rebreather wasn’t cutting it, and 6% because we wanted the place the nasal gastric tube).

So what happened to these patients?

See the diagram and figures in the show notes.

Essentially the outcomes were: all but two of the patients either improved their sats for stayed at the hundred percent in the case of de-nitrogenation

. . . .

There were no complications. Two patients avoided intubation (in the paper we took great pains to say that we don’t recommend you use DSI to avoid intubation but the speaker says you probably can’t it’s just that you can’t use his paper to defend your outcome if unfortunate).

The classic case in the study of the above is the horrible asthmatic came in and they were barely moving air. And you know if you just get them on some noninvasives [BiPAP] to push the nebs in, they’ll probably do okay. But they couldn’t tolerate the BiPAP and nebs.

But after the ketamine, they tolerated it beautifully. They woke up from their dissociative state 20 min. later and the clinicians involved thought that they look so good that they didn’t need intubation anymore. Instead they were admitted and watch. And neither of those [two] got innovated and they went home. But it is only two patients in the study. We’ve since done a handful more but if you do it you can’t use the paper to defend the negative outcome.

Now, the last thing I’ll talk about is what if something goes wrong? What if the patient gets an emtogenic effect from the ketamine?

Well, ketamine’s emtogenic effect in adults is post-emergent. So the only patients in which this would matter would be the patient in which you decided not to intubate them.

We don’t recommend that you not intubate but if you thought that that was what was clinically indicated, then you could give an anti-emetic. And you would need to be prepared for them to vomit when they woke up. But there is no peri-procedural emesis that I could find in the literature or in my clinical experience or in the experience of my colleagues.

Can you place noninvasive [BiPAP] on a patient with the altered mental status of DSI? And the answer in my mind is yes if it is ketamine.

The answer is probably yes regardless of what you’re using if you’re watching the patient in DSI. And you should be doing that and being with the patient continuously during the DSI. With ketamine you definitely can and again you don’t leave the room for the 3 min. while they are pre-oxygenating with the BVM with a PEEP valve, with the noninvasive, or with the new ventilator mask and you watch them. And I think our study bore that out.

What if the patient is hypertensive or tachycardic? This is a question that needs an answer.

We did not give any patients who were markedly tachycardic or hypertensive any ketamine in this study. I believe, that without proof, that if you did give ketamine to these patients of their vital signs would actually get better. That is been my experience. When they are already in sympathetic surge ketamine makes their vitals better not worse. But this needs to be studied.

So the next question is can we do this with other medications?

Can I do this with propofol; can I do this with etomidate? Can I do this with midazolam?

The answer is you probably could but I don’t know what dose you would use.

And that’s because the beauty of ketamine is that in the critically ill patient there is an enormous dosage range of safety.

The agent that I’d really like to be able to use for the patient with high blood pressure or high pulse rate and works beautifully is droperidol. The patient is still wherewith droperidol so you have to give an induction agent before you paralyze them. It will work with DSI but it isn’t available.

The last thing to talk about is what about the patient who goes apneic?

Well again ketamine shouldn’t do that in adults. And we’ve not seen case reports except for one in which there’ll bunch of other issues that clouded things. And it can cause apnea if you push it rapidly but that’s only for 15 seconds and then they’ll start breathing again.

But what if you are the first case [with ketamine] of apnea with DSI?

Well, what you do when you do DSI is – – you have every piece of equipment that you will need for airway management ready to go. You’ll have every medicine you’ll need for the intubation and for the post intubation and you’ll have pulse dose epinephrine ready in case they become hypotensive [see blog post on pulse dose epinephrine in adults]. You’ll have everything you need for the difficult airway. You’ll have the BVM ready you’ll have your suction ready.

You’ll have all the above in place before you push the ketamine. You not believe the room. You can be watching the patient throughout the DSI preoxygenation.

And if they do go apneic, push your rocuronium or push your succinylcholine and intubate them.

You are in exactly the same situation as if you had RSIed them.

What about ketamine induced laryngospasm in adults?

I don’t think this situation exists but people told me that it does. If ketamine induced adult laryngospasm does happen then you push a muscle relaxant and again you’re in the same position you would be if you had RSIed them.

So DSI is just procedural sedation and the procedure is preoxygenation. (Min’s Pharmacology blog will discuss all this further).